The fundamental mode characteristics of hybrid metal‐insulator‐metal plasmonic waveguide (HMIMPW), consists of a high‐index layer sandwiched between two spacer/low‐index and metal layers, has been explored to achieve relatively high power density with smaller effective mode area in low‐index waveguide region at the wavelength of 1550 nm. The HMIMPW has the advantage of low power loss with relatively large propagation distance, of order of several tens of λ. The simulation results have demonstrated that with spacer thickness of 10 nm, significantly higher confinement of optical mode power (> 65%) can be realized in the spacer region of HMIMPW with relatively smaller effective area of 0.0060 μm2 together with the power density > 200 μm−2. This type of analysis and results are very desirable for several specific applications, like optical sensing, nonlinear optics, optical manipulations. Further, the investigations on crosstalk performance between two parallel HMIMPWs have been addressed in order to realize the high integration density over the photonic chip. The decoupling separation of nearly 560 nm has been accomplished with the thicknesses of low‐ and high‐index regions, respectively, of 10 and 50 nm.

No abstract

No abstract

Slot waveguide has emerged as a potential candidate for the design of evanescent field absorption based photonic gas sensors, optical quantum information applications, etc. In this paper, three different slot waveguide structures, i.e., conventional slot, partial-strip-loaded slot, and full-strip-loaded slot waveguides have been explored to analyze their sensing performance for the methane gas. As the methane gas has the peak absorption at around 3.31 µm, therefore, this has been considered as the operating wavelength for the analysis. In anticipation of improvement in evanescent field ratio in slot region and hence, the sensing capabilities of the gas sensor, the slot waveguide structures have been designed by depositing the germanium layer over the calcium fluoride in different manners. To realize the significant evanescent field and sensitivity along with relatively low propagation loss, the suitable dimension of the slot waveguide structures has been chosen very judiciously. Several waveguide parameters, such as evanescent field ratio, propagation loss, and sensitivity have been chosen for the analysis and comparison of slot waveguide structures, by varying the arm-width and thickness of germanium layer. Simulation results have demonstrated that the full-striploaded slot waveguide has the superior performance in terms of higher evanescent field and higher sensitivity, which is followed by the partial-strip-loaded slot waveguide, even for the fixed target value of propagation loss. Moreover, the current analysis may be extended for the design of suitable photodetector that can further enhance the performance of the gas sensor.

A metal-cap wedge shape hybrid plasmonic waveguide (WSHPW) has been investigated, for the nano-scale light confinement and long propagation range, in order to analyze the optical properties, such as propagation length, normalized effective mode area, etc., of the fundamental hybrid mode at the wavelength of 1550 𝑛𝑚. Due to the wedge shape structure of high-index region (AlGaAs), the energy is mostly confined at the top of it, inside the low-index region. This results in significant improvement in the propagation length. The modal analysis has been done, using the finite element method, by varying the width of waveguide, wedge angle, permittivity of high-and low-index regions, and heights of metal, high-and low-index regions. The analysis has been further extended for different metal, such as Silver (Ag), Gold (Au) and Aluminum (Al). From the simulation results, it has been established that the propagation length (𝐿 𝑝 ) > 490 𝜇𝑚, can be achieved for the fundamental mode propagation. Further, the investigations on coupling length (𝐿 𝑐 ) between the two parallel WSHPWs have been done, which has been achieved as small as 6.10 𝜇𝑚, for the waveguide separation of 100 𝑛𝑚, and waveguide width of 50 𝑛𝑚.